Inverted Microcontact Printing on Polystyrene-block-Poly(tert-butyl acrylate) Films; A Versatille Approach to Fabricate Structured Biointerfaces Across the Length Scale

The combination of the recently introduced soft lithographic technique of inverted microcontact printing (i-μCP) and spin-coated films of polystyrene-block-poly(tert-butyl acrylate) (PS690-b-PtBA1210) as a reactive platform is shown to yield a versatile approach for the facile fabrication of topographically structured and chemically patterned biointerfaces with characteristic spacings and distances that cross many orders of magnitude. The shortcomings of conventional μCP in printing of small features with large spacings, due to the collapse of small or high aspect ratio stamp structures, are circumvented in i-μCP by printing reactants using a featureless elastomeric stamp onto a topographically structured reactive polymer film. Prior to molecular transfer, the substrate-supported PS690-b-PtBA1210 films were structured by imprint lithography resulting in lateral and vertical feature sizes between >50 μm−150 nm and >1.0 μm−18 nm, respectively. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and water contact angle measurements provided evidence for the absence of surface chemical transformations during the imprinting step. Following the previously established hydrolysis and activation protocol with trifluoroacetic acid and N-hydroxysuccinimide, amino end-functionalized poly(ethylene glycol) (PEG-NH2), as well as bovine serum albumin and fibronectin as model proteins, were successfully transferred by i-μCP and coupled covalently. As shown, i-μCP yields increased PEG coverages and thus improved performance in suppressing nonspecific adsorption of proteins by exploiting the high local concentrations in the micro- and nanocontacts during molecular transfer. The i-μCP strategy provides access to versatile biointerface platforms patterned across the length scales, as shown for guided cancer cell adhesion, which opens the pathway for systematic cell−surface interaction studies